86 250r carb/jetting question

[250rRoostmaster]

hey i have a 86r with a 89 motor with the carb off a 85 250r, i am wanting a good place to start with my jetting... It runs good but seems kinda off, the only mods is a K&N airfilter with no airbox lid and a fmf silencer, i don't know if it has the original main in it or not which is a 142 if not mistaken. Is there a way to tell what size jet you have?? I'm gonna pick up some various sizes tomorrow and test it over the weekend but just wanted a good starting point. The clip is at the top and i'm running the air screw 2 turns out. Any help would be appriciated :D. I;m gonna be picking up a fmf fatty pipe and some boysen power reeds also in the near future so probably gonna need to change the jetting for that as wel....l

[bigbadktm]

i have an 85 that has a fatty pipe and silencer on it with the flat slide carb, been bored at least once?? and I am running a 162 at 40:1 for now, i might bump up to a 165 just to richen up the top end a little and prevent a lean seize. would also like to go with some power reeds, but money has been a lil tight lately

[250rRoostmaster]

Thats the next thing on the list is the power reeds then i'll get a fmf fatty

[250rRoostmaster]

How do you like the fatty on your bike??

[bigbadktm]

well i still dont have much ride time on my R, I can tell you that the FMF pipe on my KTM really woke it up. It was hard to keep the front end down in the sand once i bolted that pipe on. But on the R, I would buy one if it didnt already come with one on it. Just one of the first upgrades on the list.

I think that the reeds are gonna be my next purchase as well, it seems to sputter a lil on the top end and I think that it might be the reeds not doing their job.

[250rRoostmaster]

Just kinda wondering since it's an 89 motor with an 85 carb that maybe i should jet it up according to the 86 carb specs

[250rRoostmaster]

Anybody else??

[ceaserthethird]

Get a PWK 38mm carb, the '85 carbs are junk.

Try e-GaY

[250rRoostmaster]

Well i know they're not the best but for now i have to use it... So should i jet like the 86??

[Mosh]

The 85 round slide carb had a inherant problem with being too rich.
I have heard all kinds of reasons why, but the most common reason is fuel is sucked up through the main jet when it is not needed.

You wont be able to jet that 85 carb to any of the newer years specs, becuase the carbs on the 85 are a whole different design.

As stated above, a PWK 38 carb is the best design for those, but also you could grab a 86 and up Kehin PJ 34 from any of the stock TRX quads and use that carb..It will be cheaper than the PWK, and run better and easier to tune vs. the 85 carb.If you do go with the PJ carb you will also need the cable for that carb.The 85 cable wont work.

Your second best bet would be to step down the 85 carb to maybe a 160 or even a 158 main if they offer that size for that carb, and recheck your plug and see if the sputtering clears up. But make sure with each jet change you do a plug chop to make sure you do not lean the engine too much.
I have "heard" some guys have had to go down to the 140's even 130's to get a 85 carb to perform good.
They were just poorly designed and too rich out of the box.

You reeds are probably not the problem but they probably are due for replacement just for maintenance. Generally reeds will suffer down low and in the mid range if they are worn out, and they wont idle good if they are broken or weak.

Also make sure you have a new plug in it before tuning it, as plugs will run good down low and in the middle, but break up under hi RPM's if they are partially fouled out.

[250rRoostmaster]

The 85 round slide carb had a inherant problem with being too rich.
I have heard all kinds of reasons why, but the most common reason is fuel is sucked up through the main jet when it is not needed.

You wont be able to jet that 85 carb to any of the newer years specs, becuase the carbs on the 85 are a whole different design.

As stated above, a PWK 38 carb is the best design for those, but also you could grab a 86 and up Kehin PJ 34 from any of the stock TRX quads and use that carb..It will be cheaper than the PWK, and run better and easier to tune vs. the 85 carb.If you do go with the PJ carb you will also need the cable for that carb.The 85 cable wont work.

Your second best bet would be to step down the 85 carb to maybe a 160 or even a 158 main if they offer that size for that carb, and recheck your plug and see if the sputtering clears up. But make sure with each jet change you do a plug chop to make sure you do not lean the engine too much.
I have "heard" some guys have had to go down to the 140's even 130's to get a 85 carb to perform good.
They were just poorly designed and too rich out of the box.

You reeds are probably not the problem but they probably are due for replacement just for maintenance. Generally reeds will suffer down low and in the mid range if they are worn out, and they wont idle good if they are broken or weak.

Also make sure you have a new plug in it before tuning it, as plugs will run good down low and in the middle, but break up under hi RPM's if they are partially fouled out.
Its got the stock 142 main in it now and i was thinking of going to a 148 or 150 in case it's running rich

[Dirtcrasher]

If they (85) are inherently rich, I agree, drop down some sixes and do some plug chops/viewing.

I STILL have not got my 87 200X running perfect. I spend hours and hours, then the temp drops and everything changes. I know it's not a 2 stroke so you have to be allot more careful than I do. I think my race cam is what it is, never a trail trike, just a 108 octane monster up top speed. In my case I may have to grab a less aggressive cam......

Like the others said, just make certain that the plug is new either NOW or during jetting and unfortunately the best cost I can seem to get om mains is about 3.50 a pop plus shipping. I can be a very long and tough task.

Your clip is at the top (leanest), maybe thats what it calls for, IDK?? But I'd get it in the center groove and play with the main. That is unless 1/4 to 3/4 throttle is affected but then again, just changing the main affects how that needle reacts.

If the 85 carb is a bum deal, it may be cheaper to grab the correct carb than to buy a bunch of jets for your 85 carb people don't seem to like anyhow....... I bought about 100$ worth of jets to get my 87X correct and it's still not there like it should be...... It is great to have a big stash of jets though; You'll always need them if your like 80% of us........

I wonder if even ONE of us enjoys jetting? About the only time I did enjoy it was on the 350X with a SuperTrapp and a couple steps up on the main. Some guys get it in a couple hours but when you make DRASTIC changes it can take some time. Don't ride it too much unless you know it's rich and of course, the fuel/oil mix all play a roll in this too. Whats your mix and the of oil for pre-mix??

Once it's right, it's great. Power and torques everywhere the airbox and exhaust want it to be.... Those K+N filters breath really well esp. if the lid is off so b careful.

[250rRoostmaster]

Running lean i meant

[250rRoostmaster]

I'm running 32:1 blendzall with 92 octane gas

[Dirtcrasher]

If it's lean, the clip on the bottom is not a good starting point, the book may say second clip down or middle; Who knows?............. But raise that clip! It will richen up 1/4-3/4 throttle and plays a role in WOT too........

[Mosh]

Running lean i meant
When they lean out, they usually rev to the moon real nice and clean, but lose torque.

If it is breaking up on the top end, you are too rich, or losing spark.

Make sure your air filter is not over oiled too.

[250rRoostmaster]

Thanks i'm gonna ride this weekend so i'll check it all out, probably gonna go from the 142 main to a 148 or 150 main just to see how it reacts and i moved the needle clip down 1 position